﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Claims;
using System.Threading.Tasks;
using System.Web;
using System.Web.Mvc;
using Microsoft.Owin.Security;
using Microsoft.Owin.Security.Cookies;
using OpenIddict.Client;
using OpenIddict.Client.Owin;
using static OpenIddict.Abstractions.OpenIddictConstants;

namespace OpenIddict.Sandbox.AspNet.Client.Controllers;

public class AuthenticationController : Controller
{
    private readonly OpenIddictClientService _service;

    public AuthenticationController(OpenIddictClientService service)
        => _service = service;

    [HttpPost, Route("~/login"), ValidateAntiForgeryToken]
    public async Task<ActionResult> LogIn(string provider, string returnUrl)
    {
        var context = HttpContext.GetOwinContext();

        // The local authorization server sample allows the client to select the external
        // identity provider that will be used to eventually authenticate the user. For that,
        // a custom "identity_provider" parameter is sent to the authorization server so that
        // the user is directly redirected to GitHub (in this case, no login page is shown).
        if (string.Equals(provider, "Local+GitHub", StringComparison.Ordinal))
        {
            var properties = new AuthenticationProperties(new Dictionary<string, string>
            {
                // Note: when only one client is registered in the client options,
                // specifying the issuer URI or the provider name is not required.
                [OpenIddictClientOwinConstants.Properties.ProviderName] = "Local",

                // Note: the OWIN host requires appending the #string suffix to indicate
                // that the "identity_provider" property is a public string parameter.
                [Parameters.IdentityProvider + OpenIddictClientOwinConstants.PropertyTypes.String] = "GitHub"
            })
            {
                // Only allow local return URLs to prevent open redirect attacks.
                RedirectUri = Url.IsLocalUrl(returnUrl) ? returnUrl : "/"
            };

            // Ask the OpenIddict client middleware to redirect the user agent to the identity provider.
            context.Authentication.Challenge(properties, OpenIddictClientOwinDefaults.AuthenticationType);
            return new EmptyResult();
        }

        else
        {
            // Note: OpenIddict always validates the specified provider name when handling the challenge operation,
            // but the provider can also be validated earlier to return an error page or a special HTTP error code.
            var registrations = await _service.GetClientRegistrationsAsync();
            if (!registrations.Any(registration => string.Equals(registration.ProviderName, provider, StringComparison.Ordinal)))
            {
                return new HttpStatusCodeResult(400);
            }

            var properties = new AuthenticationProperties(new Dictionary<string, string>
            {
                // Note: when only one client is registered in the client options,
                // specifying the issuer URI or the provider name is not required.
                [OpenIddictClientOwinConstants.Properties.ProviderName] = provider
            })
            {
                // Only allow local return URLs to prevent open redirect attacks.
                RedirectUri = Url.IsLocalUrl(returnUrl) ? returnUrl : "/"
            };

            // Ask the OpenIddict client middleware to redirect the user agent to the identity provider.
            context.Authentication.Challenge(properties, OpenIddictClientOwinDefaults.AuthenticationType);
            return new EmptyResult();
        }
    }

    [HttpPost, Route("~/logout"), ValidateAntiForgeryToken]
    public async Task<ActionResult> LogOut(string returnUrl)
    {
        var context = HttpContext.GetOwinContext();

        // Retrieve the identity stored in the local authentication cookie. If it's not available,
        // this indicate that the user is already logged out locally (or has not logged in yet).
        var result = await context.Authentication.AuthenticateAsync(CookieAuthenticationDefaults.AuthenticationType);
        if (result is not { Identity: ClaimsIdentity identity })
        {
            // Only allow local return URLs to prevent open redirect attacks.
            return Redirect(Url.IsLocalUrl(returnUrl) ? returnUrl : "/");
        }

        // Remove the local authentication cookie before triggering a redirection to the remote server.
        context.Authentication.SignOut(CookieAuthenticationDefaults.AuthenticationType);

        // Extract the client registration identifier and retrieve the associated server configuration.
        // If the provider is known to support remote sign-out, ask OpenIddict to initiate a end session request.
        if (identity.FindFirst(Claims.Private.RegistrationId)?.Value is string identifier &&
            await _service.GetServerConfigurationByRegistrationIdAsync(identifier) is { EndSessionEndpoint: Uri })
        {
            var properties = new AuthenticationProperties(new Dictionary<string, string>
            {
                [OpenIddictClientOwinConstants.Properties.RegistrationId] = identifier,

                // While not required, the specification encourages sending an id_token_hint
                // parameter containing an identity token returned by the server for this user.
                [OpenIddictClientOwinConstants.Properties.IdentityTokenHint] =
                    result.Properties.Dictionary[OpenIddictClientOwinConstants.Tokens.BackchannelIdentityToken]
            })
            {
                // Only allow local return URLs to prevent open redirect attacks.
                RedirectUri = Url.IsLocalUrl(returnUrl) ? returnUrl : "/"
            };

            // Ask the OpenIddict client middleware to redirect the user agent to the identity provider.
            context.Authentication.SignOut(properties, OpenIddictClientOwinDefaults.AuthenticationType);
            return new EmptyResult();
        }

        // Only allow local return URLs to prevent open redirect attacks.
        return Redirect(Url.IsLocalUrl(returnUrl) ? returnUrl : "/");
    }

    // Note: this controller uses the same callback action for all providers
    // but for users who prefer using a different action per provider,
    // the following action can be split into separate actions.
    [AcceptVerbs("GET", "POST"), Route("~/callback/login/{provider}")]
    public async Task<ActionResult> LogInCallback()
    {
        var context = HttpContext.GetOwinContext();

        // Retrieve the authorization data validated by OpenIddict as part of the callback handling.
        var result = await context.Authentication.AuthenticateAsync(OpenIddictClientOwinDefaults.AuthenticationType);

        // Multiple strategies exist to handle OAuth 2.0/OpenID Connect callbacks, each with their pros and cons:
        //
        //   * Directly using the tokens to perform the necessary action(s) on behalf of the user, which is suitable
        //     for applications that don't need a long-term access to the user's resources or don't want to store
        //     access/refresh tokens in a database or in an authentication cookie (which has security implications).
        //     It is also suitable for applications that don't need to authenticate users but only need to perform
        //     action(s) on their behalf by making API calls using the access token returned by the remote server.
        //
        //   * Storing the external claims/tokens in a database (and optionally keeping the essential claims in an
        //     authentication cookie so that cookie size limits are not hit). For the applications that use ASP.NET
        //     Core Identity, the UserManager.SetAuthenticationTokenAsync() API can be used to store external tokens.
        //
        //     Note: in this case, it's recommended to use column encryption to protect the tokens in the database.
        //
        //   * Storing the external claims/tokens in an authentication cookie, which doesn't require having
        //     a user database but may be affected by the cookie size limits enforced by most browser vendors
        //     (e.g Safari for macOS and Safari for iOS/iPadOS enforce a per-domain 4KB limit for all cookies).
        //
        //     Note: this is the approach used here, but the external claims are first filtered to only persist
        //     a few claims like the user identifier. The same approach is used to store the access/refresh tokens.

        // Important: if the remote server doesn't support OpenID Connect and doesn't expose a userinfo endpoint,
        // result.Principal.Identity will represent an unauthenticated identity and won't contain any user claim.
        //
        // Such identities cannot be used as-is to build an authentication cookie in ASP.NET (as the
        // antiforgery stack requires at least a name claim to bind CSRF cookies to the user's identity) but
        // the access/refresh tokens can be retrieved using result.Properties.GetTokens() to make API calls.
        if (result.Identity is not ClaimsIdentity { IsAuthenticated: true })
        {
            throw new InvalidOperationException("The external authorization data cannot be used for authentication.");
        }

        // Build an identity based on the external claims and that will be used to create the authentication cookie.
        //
        // By default, all claims extracted during the authorization dance are available. The claims collection stored
        // in the cookie can be filtered out or mapped to different names depending the claim name or its issuer.
        var claims = result.Identity.Claims.Where(claim => claim.Type is ClaimTypes.NameIdentifier or ClaimTypes.Name
            //
            // Preserve the registration details to be able to resolve them later.
            //
            or Claims.Private.RegistrationId or Claims.Private.ProviderName
            //
            // The ASP.NET 4.x antiforgery module requires preserving the "identityprovider" claim.
            //
            or "http://schemas.microsoft.com/accesscontrolservice/2010/07/claims/identityprovider");

        var identity = new ClaimsIdentity(claims,
            authenticationType: CookieAuthenticationDefaults.AuthenticationType,
            nameType: ClaimTypes.Name,
            roleType: ClaimTypes.Role);

        // Build the authentication properties based on the properties that were added when the challenge was triggered.
        var properties = new AuthenticationProperties(result.Properties.Dictionary
            .Where(item => item.Key is
                // Preserve the return URL.
                ".redirect" or

                // If needed, the tokens returned by the authorization server can be stored in the authentication cookie.
                OpenIddictClientOwinConstants.Tokens.BackchannelAccessToken   or
                OpenIddictClientOwinConstants.Tokens.BackchannelIdentityToken or
                OpenIddictClientOwinConstants.Tokens.RefreshToken)
            .ToDictionary(pair => pair.Key, pair => pair.Value));

        context.Authentication.SignIn(properties, identity);
        return Redirect(properties.RedirectUri ?? "/");
    }

    // Note: this controller uses the same callback action for all providers
    // but for users who prefer using a different action per provider,
    // the following action can be split into separate actions.
    [AcceptVerbs("GET", "POST"), Route("~/callback/logout/{provider}")]
    public async Task<ActionResult> LogOutCallback()
    {
        var context = HttpContext.GetOwinContext();

        // Retrieve the data stored by OpenIddict in the state token created when the logout was triggered.
        var result = await context.Authentication.AuthenticateAsync(OpenIddictClientOwinDefaults.AuthenticationType);

        // In this sample, the local authentication cookie is always removed before the user agent is redirected
        // to the authorization server. Applications that prefer delaying the removal of the local cookie can
        // remove the corresponding code from the logout action and remove the authentication cookie in this action.

        return Redirect(result.Properties.RedirectUri ?? "/");
    }
}
